Transmission Apparatus, Content Reproduction Apparatus, and Content and License Distribution System

ABSTRACT

A transmission apparatus ( 101 ) includes: a license data input unit ( 202 ) that accepts an input of license data which permits reproduction of a storage content linked from a streaming content; a multiplexer ( 204 ) that generates multiplexed data by multiplexing the inputted license data on a broadcast content for a predetermined period of time; and an output unit ( 206 ) that transmits the generated multiplexed data to a content reproduction apparatus ( 102 ) via digital broadcast. 
     The content reproduction apparatus ( 102 ) includes: a receiving unit ( 301 ) that receives multiplexed data; a demultiplexer ( 302 ) that extracts license data and a broadcast content from the received multiplexed data; and a content reproduction unit ( 307 ) that reproduces the extracted broadcast content, and when obtaining a storage content whose reproduction is permitted based on the extracted license data, reproduces the obtained storage content based on the license data by switching the reproduction from the broadcast content to the storage content.

TECHNICAL FIELD

The present invention relates to a content and license distributionsystem in which a transmission apparatus distributes contents on whichlicense data that permits reproduction of the contents is multiplexedand a content reproduction apparatus reproduces the contents. It alsorelates to such transmission apparatus and content reproductionapparatus.

BACKGROUND ART

There is a conventional content and license distribution method for acontent distribution system in which a content reproduction apparatusobtains, from a content distribution server, both a content and itslicense in which usage rules for allowing the use of the content aredescribed, as single data. For example, a patent literature 1 (JapaneseLaid-Open Patent Application No. 2000-155734 Publication) discloses amethod for downloading content data and its license as single data froma content server.

It can be assumed in the future content distribution that a content islinked with another content and a content reproduction apparatusreproduces these contents in sequence according to the link. Forexample, it is assumed that a content which places a link to anothercontent (a link source content) is a real time streaming content to bedistributed according to the schedule, while a content linked from thelink source content (a linked content) is a storage content which ispreviously downloaded to the content reproduction apparatus. It isfurther assumed that the license of the linked content is changed withthe lapse of reproduction time of the link source content. For example,it is assumed that needs for such control may grow that although a usercan reproduce the linked content only once if he/she reproduces the linksource streaming content for only 10 minutes from the beginning, he/shecan reproduce the linked content three times if he/she reproduces thelink source content for another 10 minutes.

However, in the case where the license of a storage content is changeddepending on the reproduction time of a real time streaming content tobe distributed according to the schedule, as described above, theconventional method requires obtaining, from a content server, a contenton which the license that varies depending upon the reproduction time ofthe link source content is multiplexed, which is likely to causeincrease in access to the content server for obtaining such content.Furthermore, since such link source content is a real time streamingcontent to be distributed according to the schedule, it is likely thatthe accesses to the content server for obtaining the content concentratein a specific period of time. As typically shown in the above-mentionedexample, in the case where the license of a linked content is changeddepending on a link source content, regardless of whether the linkedcontent is a streaming content or a storage content, accesses to acontent server for obtaining such content are likely to increase. So anobject of the present invention is to provide a method for solving theseproblems.

DISCLOSURE OF INVENTION

In order to solve the above problems, the transmission apparatusaccording to the present invention is a transmission apparatuscomprising: a license obtainment unit operable to obtain second licensedata that permits reproduction of a second content linked from a firstcontent; a multiplexed data generation unit operable to generatemultiplexed data by multiplexing the obtained second license data on thefirst content; and a transmission unit operable to transmit thegenerated multiplexed data to a content reproduction apparatus bystreaming for a predetermined period of time.

Alternatively, in the above transmission apparatus, the transmissionunit may further be operable to transmit multiplexed data generated bymultiplexing second license data on the first content, the secondlicense data permitting longer reproduction of the second content as anelapsed time from a start of the transmission of the multiplexed dataincluding the first content becomes longer.

Furthermore, the content reproduction apparatus according to the presentinvention is a content reproduction apparatus that is capable ofswitching reproduction of a content from a streaming content which iscurrently being reproduced to a storage content linked from thestreaming content, the apparatus comprising: a receiving unit operableto receive multiplexed data generated by multiplexing, for apredetermined period of time, second license data that permitsreproduction of a second content on a first content, the first contentbeing a streaming content and the second content being a storagecontent; an extracting unit operable to extract the second license dataand the first content from the received multiplexed data; a contentobtainment unit operable to obtain the second content whose reproductionis permitted by the extracted second license data; and a reproductionunit operable to reproduce the extracted first content, and thenreproduce the obtained second content based on the second license databy switching the reproduction from the first content to the secondcontent when the second content is obtained.

Alternatively, the above content reproduction apparatus may furthercomprises a content storage unit operable to previously store a storagecontent, wherein the content obtainment unit is operable to obtain thesecond content from the content storage unit in the case where thesecond content is stored in the content storage unit, while obtains thesecond content from a server via a communication network in the casewhere the second content is not stored in the content storage unit.

Note that not only is it possible to embody the present invention assuch content and license distribution system, but also as a single unitlike a transmission apparatus and a content reproduction apparatusincluded in the content and license distribution system, as a contentand license distribution method that include, as steps, thecharacteristic operations in such content and license distributionsystem. It is also possible to embody the present invention as programsthat cause a general-purpose computer such as a personal computer toexecute these characteristic operations for functioning. It should benoted that such programs can be distributed on a computer-readablerecording medium such as a CD-ROM and via a transmission medium such asthe Internet.

As described above, according to the present invention, in the casewhere a broadcast content and another storage content are linked andreproduction is switched from the link source broadcast content to thelinked storage content, it is possible to eliminate the flood ofaccesses to the license server for obtaining the license of the linkedstorage content by distributing, to the clients, the link sourcebroadcast content on which the license of such linked storage content ismultiplexed, even if all the clients switch the reproduction from thelink source broadcast content to the linked content simultaneously.

As further information about technical background to this application,the disclosure of Japanese Patent Application No. 2003-021068 filed onJan. 29, 2004 including specification, drawings and claims isincorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the invention. In the Drawings:

FIG. 1 is a diagram showing an outline configuration of a content andlicense distribution system according to an embodiment of the presentinvention;

FIG. 2 is a block diagram showing a structure of a transmissionapparatus shown in FIG. 1;

FIG. 3 is a block diagram showing one example of a structure of acontent reproduction apparatus;

FIG. 4 is a flowchart showing operations of the transmission apparatusshown in FIG. 2;

FIG. 5 is a diagram showing one example of data to be inputted to alicense data input unit;

FIG. 6 is a diagram showing one example of a license multiplexing rule;

FIG. 7 is a diagram showing one example of relation between license datamultiplexed according to the multiplexing rules shown in FIG. 6 andcontents to be reproduced based on the license data;

FIG. 8 is a flowchart showing operations of the content reproductionapparatus shown in FIG. 3;

FIG. 9 is a diagram showing one example of a data structure of a contentpacket;

FIG. 10 is a diagram showing one example of a data structure of alicense packet;

FIG. 11 is a diagram showing one example of license data managed by alicense recording unit shown in FIG. 3;

FIG. 12 is a flowchart showing operations performed in the contentreproduction apparatus shown in FIG. 3 during reproduction of a content;

FIG. 13 is a diagram showing one example of working key data managed bya working key management unit shown in FIG. 3;

FIG. 14 is a flowchart showing operations for switching reproduction ofa content in the content reproduction apparatus shown in FIG. 3;

FIG. 15 is a diagram showing one example of content data managed by thecontent recording unit shown in FIG. 3;

FIG. 16 is a diagram showing another example of relation between licensedata multiplexed according to the multiplexing rule and contents to bereproduced based on the license data;

FIG. 17A is a diagram showing one example of a screen image of a contentA to be reproduced during a period of time from T0 to T1;

FIG. 17B is a diagram showing one example of a display for prompting auser to input one of options indicating what to do in the case where auser is in a situation of a woman in the content A;

FIG. 17C is a diagram showing one example of a screen image of a contentB to be reproduced until the time T2 after a license ticket (LT) B isobtained;

FIG. 17D is a diagram showing one example of a display for prompting theuser to input one of options;

FIG. 18A is a diagram showing one example of a screen image to bereproduced until the time T3 after a LT C is obtained;

FIG. 18B is a diagram showing further another example of a display forprompting the user to input one of options;

FIG. 18C is a diagram showing one example of a screen image of a contentD reproduced to the end thereof after a LT D is obtained; and

FIG. 18D is a diagram showing one example of a screen image of thecontent B reproduced to the end thereof after the LT B is obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Here is a description of the embodiment of the present invention byreferring to the diagrams.

FIG. 1 is a diagram showing an outline configuration of a content andlicense distribution system according to the present embodiment. Thecontent and license distribution system according to the presentinvention is a system that allows change in content developments byswitching reproduction from a broadcast content (that corresponds to afirst content in the claims) which is being currently reproduced toanother storage content (that corresponds to a second content and athird content in the claims) linked from the first content as thereproduction time of the first content elapses. Note that a content inthe present embodiment denotes data which is obtained by digitallycompressing audio and video by a compression method such as MPEG-2 andMPEG-4 (Moving Picture Experts Group) and encrypting the compressed databy an encryption method such as AES and Triple DES, if necessary. Atransmission apparatus 101 for digital broadcasting multiplexes acontent and a license necessary for reproduction of a content andtransmits the multiplexed data to a broadcast satellite 103. In generalcases, a content and license data for allowing reproduction of thecontent are multiplexed, but in the present embodiment, license data ofanother content linked from the content is also multiplexed by timedivision. A content reproduction apparatus 102 receives a data streamfrom the broadcast satellite 103, demultiplexes the multiplexed data,and reproduces the content based on the license. Contents are stored ina content server 105, and the content reproduction apparatus 102 obtainscontent data from the content server 105 via a communication network 104such as the Internet.

The content distribution service using the present system is a servicefor providing users who subscribe in advance with an environment inwhich they can reproduce contents using the content reproductionapparatus 102. Contents to be distributed in this service are allencrypted, and the content reproduction apparatus 102 reproduces each ofthe contents after obtaining the license including the usage rules andthe decryption key of the content. In the present service, contents andlicenses are distributed in one of the following two methods: a methodusing the communication network 104 such as the Internet; and a methodusing the broadcast satellite 103. Furthermore, in the present service,link information indicating a link between a content and another contentis included in the content, and the content reproduction apparatus 102can specify the content to be reproduced next using the linkinformation.

The structures of the transmission apparatus 101 and the contentreproduction apparatus 102 according to the present embodiment areexplained below.

FIG. 2 is a block diagram showing the structure of the transmissionapparatus 101 shown in FIG. 1. As shown in FIG. 2, the transmissionapparatus 101 includes a content data input unit 201, a license datainput unit 202, a license multiplexing rule input unit 203, amultiplexer 204, a multiplexing control unit 205 and an output unit 206.The transmission apparatus 101 is an apparatus that generates a datastream to be distributed using the broadcast satellite 103. The contentdata input unit 201 is a functional unit that accepts the input ofpreviously encrypted content data and content IDs for identifying thecontents uniquely. The license data input unit 202 is a functional unitthat accepts the input of license data including link information foridentifying contents linked from inputted contents. The licensemultiplexing rule input unit 203 is a functional unit that accepts theinput of rules to be applied to multiplexing of content data and licensedata. The multiplexer 204 is a functional unit that multiplexes contentdata and license data so as to generate data streams. The multiplexingcontrol unit 205 is a functional unit that controls multiplexing of datain the multiplexer 204. The output unit 206 is a functional unit thattransmits the generated data stream to the broadcast satellite 103.Although a timer is needed to indicate the present time and measureelapsed time and the like when a license packet is multiplexed on acontent packet in time order, a transmission apparatus for digitalbroadcasting is expected to be equipped with such a timer, so it is notdescribed here by referring to the diagram.

Next, FIG. 3 is a block diagram showing one example of the structure ofthe content reproduction apparatus 102. As shown in FIG. 3, the contentreproduction apparatus 102 is capable of accepting the input from a userand switching reproduction from a content which is being currentlyreproduced to another content linked from the content. The contentreproduction apparatus 102 includes a receiving unit 301, ademultiplexer 302, a content packet processing unit 303, a contentrecording unit 304, a license packet processing unit 305, a licenserecording unit 306, a content reproduction unit 307, a working keymanagement unit 308, a reproduction control unit 309, a communicationunit 310 and a user operation input unit 311. The receiving unit 301 isa functional unit that receives a data stream transmitted from thebroadcast satellite 103. The demultiplexer 302 is a functional unit thatdemultiplexes the received data stream into a content packet and alicense packet. The content packet processing unit 303 is a functionalunit that performs data processing on the received content packet. Thecontent recording unit 304 is a functional unit having a storage area inwhich content data of storage contents are recorded. The license packetprocessing unit 305 is a functional unit that performs data processingon the received license packet. The license recording unit 306 is afunctional unit having a storage area in which license data is recorded.The content reproduction unit 307 is a functional unit that decrypts anddecodes content data so as to reproduce the content. The working keymanagement unit 308 is a functional unit that holds and manages aworking key for decrypting license data. The reproduction control unit309 is a functional unit that performs reproduction control of contents,such as judgment of whether or not reproduction of a content ispermitted, using license data. The communication unit 310 is afunctional unit that communicates with the content server 105 and thelike via the communication network 104. The user operation input unit311 is a functional unit that accepts operation inputs of the user ofthe content reproduction apparatus 102, such as switching of contents.

The processes performed in the transmission apparatus 101 and thecontent reproduction apparatus 102 for embodying the contentdistribution service using the present system are explained below inthis order.

First, the processes from generation of a data stream until transmissionthereof in the transmission apparatus 101 are explained by referring tothe flowchart in FIG. 4. FIG. 4 is a flowchart showing the operations ofthe transmission apparatus 101 shown in FIG. 2.

S401: Previously encrypted content data and its content ID are inputtedto the content data input unit 201. A content ID is identificationinformation for identifying a content uniquely.

S402: Data including link information for specifying a content (a linkedcontent) linked from the above content and license data is inputted tothe license data input unit 202. FIG. 5 is a diagram showing one exampleof data to be inputted to the license data input unit 202. The data tobe inputted to the license data input unit 202 includes the license IDfor identifying the license data, the linked content ID for identifyingthe linked content uniquely, the content obtainment information that isinformation necessary for obtaining content data, the content key fordecrypting the content and the usage rules of the content. Multiplepieces of data are given, as the input, to the license data input unit202.

FIG. 5 shows two pieces of data to be inputted to the license data inputunit 202. These data are identified by the license IDs “0×1001” and“0×1002”. The data identified by the license ID “0×1001” includeslicense data for allowing the use of the content identified by thecontent ID “0×AAAA”. The content identified by the content ID “0×AAAA”is specified as a linked content. The content data of the linked contentcan be obtained at ftp://xxx.xxx.xxx/content/0×AAAA.mpg, the content keyis “0×FF.FF” (128 bits), and the effective period from Dec. 1, 2003through Dec. 31, 2003 is set as a usage rule.

FIG. 403 (FIG. 4): The rules for multiplexing the content and thelicense are inputted to the license multiplexing rule input unit 203.FIG. 6 is a diagram showing one example of the license multiplexingrule. To be more specific, this diagram shows an example of amultiplexing rule for multiplexing two license data on the same contentin a time-staggered manner. A license multiplexing rule includes alicense ID of a license to which the rule is to be applied, a licenseerasing flag indicating the license storage limit in the contentreproduction apparatus 102 which received the license, and adistribution start time and a distribution end time indicating a periodof time in which the license can be multiplexed and distributed. Themultiplexing rules for all the licenses given in S402 in FIG. 4 aredescribed and inputted to the license multiplexing rule input unit 203.The inputted license multiplexing rules are transmitted to themultiplexing control unit 205.

FIG. 6 shows a description of the license multiplexing rule for thelicenses identified by the license IDs “0×1001” and “0×1002”. Itindicates that the license data identified by the license ID “0×1001” ismultiplexed on the data stream to be transmitted during the period from9:00:00 of Dec. 2, 2003 through 9:29:59 of Dec. 2, 2003. The license ID“0×1001” indicates that the license erasing flag for the license packetis set to “TRUE” when multiplexing. The license erasing flag “TRUE”means that the content reproduction apparatus 102 which received thelicense data cannot store the license identified by the license ID“0×1001” until another license linked from the same content is erasedfrom the content reproduction apparatus 102 if it is stored there.

S404 (FIG. 4): The multiplexing control unit 205 multiplexes the contentand the license data using the multiplexer 204 according to the licensemultiplexing rule so as to generate a data stream. Note that the licensedata is multiplexed after being encrypted by the working key shared withthe content reproduction apparatus 102 which is to receive the content.

S405 (FIG. 4): The generated data stream is transmitted from the outputunit 206.

The above is the description of the processes performed in thetransmission apparatus 101.

FIG. 7 is a diagram showing one example of relation between the licensedata multiplexed according to the multiplexing rule shown in FIG. 6 andthe content to be reproduced based on the license data. Here, it isassumed that a content A is a streaming content to be distributed viasatellite broadcast, and contents B, C and D are previously stored inthe content recording unit 304. This diagram shows that the license dataof the content D which is different from the content A but linked fromthe content A is multiplexed on the content A and distributed in apredetermined period of time (t0 to t1) during streaming distribution ofthe content A. During that period of time, in the content A which isbeing currently reproduced in the content reproduction apparatus 102, anevent for prompting a user to select whether or not the content is to beswitched to another content to be reproduced next occurs so that theuser can select one of the continued reproduction of the content A andthe switching to the reproduction of the content D. For example, in thecase where the content A is a drama or the like, “an event for promptinga user to select” means an event which predicts or explicitly indicatesthat the following plot development may change depending on the user'sselection.

Here, if the user selects switching to the reproduction of the contentD, the user operates the user operation input unit 311 to instruct thecontent reproduction apparatus 102 to switch to the reproduction of thecontent D. According to this operation, the license D is extracted fromthe multiplexed data. However, up to this point of time, the contentreproduction apparatus 102 has reproduced the content A according to thepreviously obtained license A, so the license recording unit 306 holdsthe license A. If, the license erasing flag “TRUE” is described in thelicense packet of the license D, for example, the license recording unit306 has to erase the license A therefrom. By erasing the license A fromthe license recording unit 306, the content reproduction apparatus 102can store the license D into the license recording unit 306 andreproduce the content D according to the license D.

On the other hand, if the user selects the continued reproduction of thecontent A, he/she operates the user operation input unit 311 so as toinstruct the continuation of reproduction of the content A. According tothis instruction, the license recording unit 306 erases the license Dextracted from the multiplexed data and continues to hold the license A.Therefore, the user can continue to view the content A according to thelicense A. Furthermore, in the case where the license C, the license Band the like are multiplexed on the license A and distributed insequence after the continued reproduction of the content A is selected,the user can also select continued reproduction of the content A or theswitching to the reproduction of another content such as the content Cand the content B, in the same manner as mentioned above.

As described above, by erasing unwanted one of the license extractedfrom the multiplexed data and the originally held license on acase-by-case basis, a memory area for only one license data is requiredin the license recording unit 306 for a series of a plurality ofcontents to be reproduced, and thus the memory area can be usedeffectively.

Note that in the above-mentioned case, every time a new license ismultiplexed, an event for inquiring a user about whether or not toswitch to another content occurs, but the present invention is notlimited to this method. For example, in the case were a variety oflicenses are multiplexed in time order during reproduction of a content,the license recording unit 306 may capture a new license every time thenew license is multiplexed if a user does nothing. In this case, if thelicense erasing flag is “TRUE”, the license recording unit 306 may erasethe previously held license and hold the new one.

Next, the processes, including receiving of a data stream, reproductionof a content and switching to reproduction of another linked content,performed in the content reproduction apparatus 102 are described below.

The processes performed in the content reproduction apparatus 102 from auser's reproduction start request until a content reproduction start aredescribed by referring to the flowchart in FIG. 8. FIG. 8 is a flowchartshowing the operations of the content reproduction apparatus 102 shownin FIG. 3.

When a user's content reproduction start request is inputted to the useroperation input unit 311, the content reproduction process is started.When starting the content reproduction, the user specifies the channelidentifier of the channel on which a content to be reproduced isdistributed and inputs the content reproduction start request.

S701: The content reproduction start request as well as the channelidentifier are transmitted from the user operation input unit 311. Thereproduction control unit 309 requests the receiving unit 301 to receivethe data stream that corresponds to the specified channel identifier.The receiving unit 301 receives the data stream that corresponds to thespecified channel identifier.

S702: The received data stream is transmitted from the receiving unit301 to the demultiplexer 302, and demultiplexed into a content packetand a license packet. The data stream received in the present serviceincludes the content packet and the license packet. The structures ofthe content packet and the license packet are described by referring toFIG. 9 and FIG. 10.

FIG. 9 is a diagram showing one example of the data structure of thecontent packet. The content packet includes a packet identifier, achannel identifier, a content ID and content data. The packet identifierindicates the type of the packet, and the identifier indicating acontent packet is described here. The channel identifier indicates thechannel on which the content is distributed. The content ID indicatesthe identifier for identifying the encrypted content included in thepacket. The content data contains the data of the encrypted content. Theabove is the description of the structure of the content packet.

Next, FIG. 10 is a diagram showing one example of the data structure ofthe license packet. The license packet includes a packet identifier, achannel identifier, a working key identifier, a link source content ID,a linked content ID, linked content obtainment information, a licenseerasing flag and license data. The packet identifier indicates the typeof the packet, and the identifier indicating a license packet isdescribed here. The channel identifier indicates the identifier of thechannel on which the license is distributed. The working key identifieris the information indicating the working key which encrypted thelicense. The working key is previously distributed to all users whosubscribed to the content distribution service in the present system.For example, the working key is distributed by airwaves for distributingpersonal information or the like via satellite digital broadcasting. Thelink source content ID and the linked content ID are identifiers forrespectively identifying the link source content and the linked contentuniquely. In this case, in the link source content ID, the content ID ofthe content included in the content packet multiplexed as a data streamof the same channel is described. These two types of informationindicate the link between the contents. In other words, they indicatethat a link is placed from the content identified by the link sourcecontent ID to the content identified by the linked content ID. Thelinked content obtainment information indicates from where the contentdata identified by the linked content ID is obtained. The licenseerasing flag is the information indicating the license storage limit inthe content reproduction apparatus 102. The license erasing flag “TRUE”means that the content reproduction apparatus 102 cannot store thelicense until another license linked from the same content is erasedfrom the content reproduction apparatus 102 if it is stored there. Thelicense erasing flag “FALSE” indicates that there is no limit on therecording of the license. The license data includes the usage rules ofthe content and the content key, and is encrypted by the working key.The above is the description of the structure of the license packet.

S703 (FIG. 8): The content packet demultiplexed from the data stream istransmitted to the content packet processing unit 303. The contentpacket processing unit 303 extracts the content ID from the obtainedcontent data and transmits it to the reproduction control unit 309. Italso transmits the content data extracted from the content packet to thecontent reproduction unit 307.

The processes from the receiving of the data stream until thetransmission of the content packet to the content reproduction unit 307,among the processes in S701 to S703 in FIG. 8, are continued until thereproduction of the content is finished.

S704 (FIG. 8): The reproduction control unit 309 obtains the usage rulesand the content key of the content from the license recording unit 306,using the obtained content ID. Note that it is assumed that the contentreproduction apparatus 102 previously obtains the license forreproducing the real time streaming content to be distributed accordingto the schedule and records it into the license recording unit 304. FIG.11 shows one example of data managed by the license recording unit 304.The content recording management unit 304 manages, for each license,information of a use-permitted content ID, a link source content ID, alicense ID, content obtainment information, a usage rule and a contentkey. All these information denote “license information”. Theuse-permitted content ID is an identifier for uniquely identifying acontent that is permitted to be reproduced under the license. The linksource content ID is an identifier for uniquely identifying a linksource content if another content is linked from that content. Thecontent obtainment information indicates from where the content data ofthat content is obtained. The usage rule indicates the condition to besatisfied when the content is reproduced. The content key indicates thedecryption key for the content.

FIG. 11 shows that the licenses for permitting the use of the contentsidentified by the content IDs “0×AAAA” and “0×BBBB” are recorded. Hereis a description of the license for the content identified by thecontent ID “0×BBBB”. The content ID “0×BBBB” is linked from the contentID “0×2222”. The license of the content ID “0×BBBB” is the license ID“0×2002”, no usage rule is set, and the content key is “0×AA . . . AA”(128 bits). The content identified by the content ID “0×BBBB” isbroadcasted as a scheduled streaming content on the channel identifiedby the channel ID “0×01” from 13:00:00 of Dec. 24, 2003 through 15:00:00of that day. The content identified by the use-permitted content ID“0-×BBBB” is the content D in the case of FIG. 7, while the contentidentified by the link source content ID “0×2222” is the content A. Thelicense identified by the license ID “0×2002” is the license D in thecase of FIG. 7, which is multiplexed on the content A identified by thelink source content ID “0×2222” and distributed during the period fromt0 (Dec. 1, 2003) to t1 (Dec. 31, 2003). This license is identical to anew license A which is stored in the license recording unit 306 afterthe license A for reproducing the content A is erased from the licenserecording unit 306.

S705 (FIG. 8): The reproduction control unit 309 evaluates the usagerule of the obtained content and judges whether or not the content ispermitted to be reproduced. If it judges that the reproduction ispermitted, it transmits the content key to the content reproduction unit307, updates the content usage rule, if necessary, and then moves to thenext process S706 in FIG. 8. The update of the license denotes thatupdating the value described in the current license information into thevalue obtained by subtracting 1 from the current value, in the casewhere the usage rule is the permitted number of reproductions. When thereproduction control unit 309 judges that the reproduction is notpermitted, it notifies the user that no more reproduction is permittedand terminates the process.

S706 (FIG. 8): The content reproduction unit 307 decrypts the contentdata using the content key and reproduces the content.

The above is the description of the processes performed in the contentreproduction apparatus 102, from the user's reproduction start requestup to the start of the content reproduction.

Next, the processes performed in the content reproduction apparatus 102during reproduction of a content is described below.

The processes performed in the content reproduction apparatus 102 duringreproduction of a content is described by referring to the flowchart inFIG. 12. FIG. 12 is a flowchart showing the operations performed in thecontent reproduction apparatus 102 during reproduction of a content.

S1101: The receiving unit receives the data stream on the currentchannel, and transmits it to the demultiplexer 302.

S1102: The demultiplexer 302 demultiplexes the data stream into acontent packet and a license packet.

S1103: According to the packet type, the demultiplexed content packet istransmitted to the content packet processing unit 303, which reproducesthe content (S1109), while the demultiplexed license packet istransmitted to the license packet processing unit 305, which decryptsthe license (51104).

S1104: The license packet processing unit 305 which has received thelicense packet obtains the working key from the working key managementunit 308 using the working key identifier in the license packet. Thedata managed by the working key management unit 308 is described later.The license packet processing unit 305 decrypts the license in thelicense data using the working key obtained from the working keymanagement unit 308, and transmits the decrypted license to the licenserecording unit 306. The content reproduction apparatus 102 previouslyobtains the working key required for the decryption of the license viabroadcasting and the Internet by a secure method for preventing anytampering and tapping by a third party.

The data managed by the working key management unit 308 is describedbelow. FIG. 13 shows one example of the data managed by the working keymanagement unit 308. The working key management unit 308 manages workingkey identifiers for identifying working keys uniquely and actual data ofthe working keys. FIG. 13 shows that two working keys are managed. Hereis a description of the data of the working key identifier “0×1234”. Theactual data of the working key identifier “0×1234” is “0×1111 . . .1111” (128 bits). The above is the description of the data managed bythe working key management unit 308.

S1105 (FIG. 12): The license packet processing unit 305 checks thelicense erasing flag in the license packet. When the license erasingflag is TRUE, it performs the process of S1106 in FIG. 12. When thelicense erasing flag is FALSE, it performs the process of S1107 in FIG.12.

S1106 (FIG. 12): In the case where there exists, in the licenserecording unit 306, the license of the link source content ID same asthe link source content ID in the license packet obtained in S1104 inFIG. 12, the license packet processing unit 305 deletes that license inthe license recording unit 306.

S1107 (FIG. 12): It records the license decrypted in the S1104 in FIG.12 into the license recording unit 306.

S1108 (FIG. 12): The license packet processing unit 305 notifies theuser that the link destination of the content has been updated, andterminates the process.

S1109 in FIG. 12: The content packet processing unit 303 extracts thecontent data from the obtained content packet, and transmits it to thecontent reproduction unit 307. The content reproduction unit 307decrypts the received content and continues to reproduce the content.

The above is the description of the processes performed in the contentreproduction apparatus 102 during reproduction of a content.

Next, the processes for switching to reproduction of a linked contentusing link information of a current content which is being reproducedare described below. Note that the following describes the case wherethe license erasing flag indicates FALSE, where a license forreproducing a linked content multiplexed on a current content is storedin the license recording unit 306 at the point of time when it isdistributed.

The processes for switching to reproduction of a linked content in thecontent reproduction apparatus 102 are described by referring to theflowchart in FIG. 14. FIG. 14 is a flowchart showing the operations forswitching reproduction of a content in the content reproductionapparatus 102.

In the content reproduction apparatus 102, a linked content reproductionrequest is inputted to the user operation input unit 311 by the userduring reproduction of a link source content.

When the reproduction request of the content linked from the currentcontent which is being reproduced is inputted to the user operationinput unit 311, the process for switching to the content to bereproduced starts. The user specifies the content ID of the content tobe reproduced when the reproduction of the linked content is started.

S1301: The user operation input unit 311 transmits the contentreproduction request as well as the content ID specified by the user tothe reproduction control unit 309. The reproduction control unit 309transmits the received content ID to the license recording unit 306, andobtains the license information concerning the specified content.

S1302: The reproduction control unit 309 evaluates the usage rule of thelicense obtained from the license recording unit 306, and judges whetheror not reproduction of the content is permitted. When it judges that thereproduction is permitted, it transmits the content key to the contentreproduction unit 307 and performs the process of S1303. When it judgesthat the reproduction is not permitted, it notifies the user that theusage rule is not satisfied, and terminates the process.

S1303: When the linked content is a storage content, the reproductioncontrol unit 307 checks whether or not there exists the content data inthe content recording unit 304. FIG. 15 shows one example of contentdata managed by the content recording unit 304. The content recordingunit 304 manages content IDs and content data. FIG. 15 shows that twocontent data are managed, and their content IDs are “0×AAAA” and“0×ZZZZ”. When there are those content data in the content recordingunit 304, it performs the process of S1305. When there is no suchcontent data in the content recording unit 304 and the linked content isa scheduled streaming content, it performs the process of S1304.

S1304: The reproduction control unit 309 obtains the content data byreferring to the “content obtainment information” in the licenseinformation obtained from the license recording unit 306.

If the linked content is a storage content, the reproduction controlunit 309 obtains the content data from the content server 105 via thecommunication unit 310, and records it into the content recording unit304.

If the linked content is a scheduled streaming content, the reproductioncontrol unit 309 specifies the channel identifier and requests thereceiving unit 301 to receive the data stream identified by thespecified channel identifier. After receiving the data stream, ittransmits the content data to the content reproduction unit 307 via thedemultiplexer 302 and the content packet processing unit 303.

S1305: If the linked content is a storage content, the reproductioncontrol unit 309 causes the content recording unit 304 to transmit thecontent data to the content reproduction unit 307.

If the linked content is a scheduled streaming content, the receivingunit 301 receives the data stream, and then transmits it to the contentreproduction unit 307 via the demultiplexer 302 and the content packetprocessing unit 303.

The content reproduction unit 307 decrypts the content data using thecontent key and reproduces the content.

The above is the description of the processes for switching toreproduction of a linked content using link information of a currentcontent which is being reproduced.

Note that the above is the description of the case where other contentsare sequentially linked from one multi-story content, but the followingis the description of another case where other multi-story contents arefurther linked from such linked content, by referring to FIGS. 16, 17and 18. FIG. 16 is a diagram showing another example of relation betweenlicense data multiplexed according to a multiplexing rule and contentsto be reproduced based on the license data. FIG. 17A is a diagramshowing one example of a screen image of a content A to be reproducedduring a period of time from T0 to T1. For example, this diagram shows asetting in which a big dragonfly is coming up to a woman who is hiking.As shown in FIG. 1.6, a license ticket (LT) B that allows reproductionof a content B is multiplexed on the content A and distributed duringthe period of time from T1 to T2. FIG. 17B is a diagram showing oneexample of a display for prompting a user to input one of optionsindicating what to do in the case where the user is in a situation ofthe woman in the content A. As shown in this diagram, during the periodfrom T1 to T2, a screen for asking the user whether or not he/she wouldlike to select switching to the content B is displayed, in conjunctionwith the distribution of the LT B. The display prompts the user toselect one of the following: 1. Catch the dragonfly; and 2. Let thedragonfly go. This display does not need to be represented by text only,but voice assist may be used, or a telop may be run as the plot on thescreen develops. Assuming that the selection of “2. Let the dragonflygo” in FIG. 17B corresponds to the selection of switching to the contentB, the LT A in the license recording unit 306 is erased, the LT B isobtained, and the reproduction is switched from the content A to thecontent B. When the user selects the switching to the content B, thelicense A for reproducing the content A in the license recording unit306 is erased if the license erasing flag is TRUE, so the user whoselected the switching to the content B cannot reproduce the content Aagain.

FIG. 17C is a diagram showing one example of the screen image of thecontent B to be reproduced until the time T2 after the LT B is obtained.For example, this diagram shows the screen image in which the dragonflyis flying off. A LT C that allows reproduction of a content C ismultiplexed on the content B and distributed during a period of timefrom T2 to T3. FIG. 17D is a diagram showing one example of a displayfor prompting the user to input one of options. The display prompts theuser to select one of the following: 1. Not follow the dragonfly; and 2.Follow the dragonfly. Assuming that the selection of “2. Follow thedragonfly” in FIG. 17D corresponds to the selection of switching to thecontent C, the LT B in the license recording unit 306 is erased, the LTC is obtained, and the reproduction is switched from the content B tothe content C.

FIG. 18A is a diagram showing one example of a screen image to bereproduced until the time T3 after a LT C is obtained. For example, thisdiagram shows the screen image in which the woman meets her collegeclassmate while she is following the dragonfly. A LT D that allowsreproduction of a content D is multiplexed on the content C anddistributed during a period of time from T3 to T4. FIG. 18B is a diagramshowing further another example of a display for prompting the user toinput one of options. The display prompts the user to -select one of thefollowing: 1. Go home because of something to do; and 2. Have tea withhim. Assuming that the selection of “2. Have tea with him” in FIG. 18Bcorresponds to the selection of switching to the content D, the LT C inthe license recording unit 306 is erased, the LT D is obtained, and thereproduction is switched from the content C to the content D.

FIG. 18C is a diagram showing one example of the screen image of thecontent D reproduced to the end thereof after the LT D is obtained. Forexample, this diagram shows the screen image in which as a result thatthe woman has tea with her college classmate, they get along with eachother and get married, have a child and have a good time with the childin a park. FIG. 18D is a diagram showing one example of the screen imageof the content B reproduced to the end thereof after the LT B isobtained. This is the screen image reproduced in the case where the userselects “1. Not follow the dragonfly” in FIG. 17D, and in this image,for example, the woman is playing with her dog at home after hiking.

Note that the above is a description in the case where linked contentshave some kind of relation with each other by taking, as an example,multi-story contents each of which has a different plot development andending, but the contents in the present invention are not limited tosuch multi-story contents, or do not need to have any relation with eachother. For example, it is possible to multiplex, on a link sourcecontent which a company wants to advertise, a license that allows a userwho reproduced the link source content for 10 minutes or longer toreproduce another linked popular content for 30 minutes more than a userwho reproduced the link source content for shorter than 10 minutes,according to the reproduction time of the link source content.

FIG. 5 shows the case where the effective period in which reproductionof a content is permitted and the permitted number of reproductions of acontent are described as the usage rules. However, it is also possibleto describe, in addition to these rules, any other restrictive rules ofcontent reproduction, such as the maximum time in which reproduction ofa content is permitted in total and the region code of a reproductionapparatus.

Note that in S1304 in FIG. 14, the data of the storage content obtainedfrom the content server 105 may include a content packet of a contentand a license packet of another content, like data to be distributedaccording to the schedule. If the data obtained from the content server105 includes such license packet, the communication unit 310 transmitsthe received data to the demultiplexer 302 in S1304 in FIG. 14. Thedemultiplexer 302 demultiplexes the received data, and then transmitsthe demultiplexed content packet to the content packet processing unit303 and the demultiplexed license packet to the license packetprocessing unit 305, respectively. The license packet processing unit305 performs the same process as the process in S1104 in FIG. 12 afterthe license is transmitted thereto. The content packet processing unit303 extracts the content data and records it into the content recordingunit 304. After completing the processes for the content packet and thelicense packet, the processes in and after S1305 in FIG. 14 follow.

Although only an exemplary embodiment of this invention has beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiment without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The content distribution method according to the present invention isuseful as a digital content distribution method and the like. Thecontent reproduction apparatus according to the present invention isuseful as a personal computer, a personal digital assistant (PDA), acellular phone, a set top box (STB) and the like having the digitalbroadcast receiving function and the communication function. Thetransmission apparatus according to the present invention is useful as atransmission apparatus and a server for a broadcast station thatdistribute contents and licenses to the content reproduction apparatusvia a communication network such as a satellite broadcasting network andthe Internet.

1. A transmission apparatus comprising: a license obtainment unitoperable to obtain second license data that permits reproduction of asecond content linked from a first content; a multiplexed datageneration unit operable to generate multiplexed data by multiplexingthe obtained second license data on the first content; and atransmission unit operable to transmit the generated multiplexed data toa content reproduction apparatus by streaming for a predetermined periodof time.
 2. The transmission apparatus according to claim 1, whereinsaid transmission unit is further operable to transmit multiplexed datagenerated by multiplexing second license data on the first content, thesecond license data permitting longer reproduction of the second contentas an elapsed time from a start of the transmission of the multiplexeddata including the first content becomes longer.
 3. The transmissionapparatus according to claim 1, wherein a third content is furtherlinked from the first content, and said transmission unit is operable totransmit multiplexed data generated by sequentially multiplexing forpredetermined periods of time, on the first content, the second licensedata that permits reproduction of the second content and third licensedata that permits reproduction of the third content.
 4. The transmissionapparatus according to claim 3, wherein in the case where the contentreproduction apparatus is permitted to store license data, saidtransmission unit is operable to transmit the multiplexed data includinga flag indicating prohibition of storing two or more license data ofcontents linked from a same content.
 5. A content reproduction apparatusthat is capable of switching reproduction of a content from a streamingcontent which is currently being reproduced to a storage content linkedfrom the streaming content, said apparatus comprising: a receiving unitoperable to receive multiplexed data generated by multiplexing, for apredetermined period of time, second license data that permitsreproduction of a second content on a first content, the first contentbeing a streaming content and the second content being a storagecontent; an extracting unit operable to extract the second license dataand the first content from the received multiplexed data; a contentobtainment unit operable to obtain the second content whose reproductionis permitted by the extracted second license data; and a reproductionunit operable to reproduce the extracted first content, and thenreproduce the obtained second content based on the second license databy switching the reproduction from the first content to the secondcontent when the second content is obtained.
 6. The content reproductionapparatus according to claim 5, further comprising a content storageunit operable to previously store a storage content, wherein saidcontent obtainment unit is operable to obtain the second content fromsaid content storage unit in the case where the second content is storedin said content storage unit, while obtains the second content from aserver via a communication network in the case where the second contentis not stored in said content storage unit.
 7. The content reproductionapparatus according to claim 5, wherein a third content is linked fromthe first content, said receiving unit is further operable to receivemultiplexed data (i) which is generated by sequentially multiplexing forpredetermined periods of time, on the first content, the second licensedata that permits reproduction of the second content and third licensedata that permits reproduction of the third content, and (ii) whichincludes a flag indicating prohibition of storing two or more licensedata multiplexed on one content, said content reproduction apparatusfurther comprises: a license storage unit operable to store onlyextracted latest license data according to the flag; and a switchinginstruction acceptance unit operable to accept an input of a user'sinstruction to switch reproduction from the first content to anothercontent, and said content obtainment unit is operable to obtain thesecond content or the third content whose reproduction is permitted bylicense data stored in said license storage unit when the user'sinstruction is accepted.
 8. The content reproduction apparatus accordingto claim 5, wherein a third content is linked from the first content,said receiving unit is further operable to receive multiplexed datawhich is generated by sequentially multiplexing for predeterminedperiods of time, on the first content, the second license-data thatpermits reproduction of the second content and third license data thatpermits reproduction of the third content, said content reproductionapparatus further comprises a switching instruction acceptance unitoperable to accept an input of a user's instruction to switchreproduction from the first content to another content, and said contentobtainment unit is operable to obtain the second content or the thirdcontent whose reproduction is permitted by the second license data orthe third license data extracted when the user's instruction isaccepted.
 9. A content and license distribution system comprising atransmission apparatus and a content reproduction apparatus, whereinsaid transmission apparatus includes: a license obtainment unit operableto obtain second license data that permits reproduction of a secondcontent linked from a first content; a multiplexed data generation unitoperable to generate multiplexed data by multiplexing the obtainedsecond license data on the first content; and a transmission unitoperable to transmit the generated multiplexed data to said contentreproduction apparatus by streaming for a predetermined period of time,and said content reproduction apparatus includes: a receiving unitoperable to receive, from said transmission apparatus, the multiplexeddata generated by multiplexing the second license data on the firstcontent, within the predetermined period of time; an extracting unitoperable to extract the second license data and the first content fromthe received multiplexed data; a content obtainment unit operable toobtain the second content whose reproduction is permitted by theextracted second license data; and a reproduction unit operable toreproduce the extracted first content, and then reproduce the obtainedsecond content based on the second license data by switching thereproduction from the first content to the second content when thesecond content is obtained.
 10. A transmission method comprising:obtaining second license data that permits reproduction of a secondcontent linked from a first content; generating multiplexed data bymultiplexing the obtained second license data on the first content; andtransmitting the generated multiplexed data to a content reproductionapparatus by streaming for a predetermined period of time.
 11. A contentreproduction method in which reproduction of a content can be switchedfrom a streaming content which is currently being reproduced to astorage content linked from the streaming content, said methodcomprising: receiving multiplexed data generated by multiplexing, for apredetermined period of time, second license data that permitsreproduction of a second content on a first content, the first contentbeing a streaming content and the second content being a storagecontent; extracting the second license data and the first content fromthe received multiplexed data; obtaining the second content whosereproduction is permitted by the extracted second license data.; andreproducing the extracted first content, and then reproducing theobtained second content based on the second license data by switchingthe reproduction from the first content to the second content when thesecond content is obtained.
 12. A program for a transmission apparatus,said program causing a computer to execute: obtaining second licensedata that permits reproduction of a second content linked from a firstcontent; generating multiplexed data by multiplexing the obtained secondlicense data on the first content; and transmitting the generatedmultiplexed data to a content reproduction apparatus by streaming for apredetermined period of time.
 13. A program for a content reproductionapparatus that is capable of switching reproduction of a content from astreaming content which is currently being reproduced to a storagecontent linked from the streaming content, said program causing acomputer to execute: receiving multiplexed data generated bymultiplexing, for a predetermined period of time, second license datathat permits reproduction of a second content on a first content, thefirst content being a streaming content and the second content being astorage content; extracting the second license data and the firstcontent from the received multiplexed data; obtaining the second contentwhose reproduction is permitted by the extracted second license data;and reproducing the extracted first content, and then reproducing theobtained second content based on the second license data by switchingthe reproduction from the first content to the second content when thesecond content is obtained.
 14. A computer-readable recording medium onwhich a program is recorded, said program causing a computer to execute:obtaining second license data that permits reproduction of a secondcontent linked from a first content; generating multiplexed data bymultiplexing the obtained second license data on the first content; andtransmitting the generated multiplexed data to a content reproductionapparatus by streaming for a predetermined period of time.
 15. Acomputer-readable recording medium on which a program is recorded, saidprogram causing a computer to execute: receiving multiplexed datagenerated by multiplexing, for a predetermined period of time, secondlicense data that permits reproduction of a second content on a firstcontent, the first content being a streaming content and the secondcontent being a storage content; extracting the second license data andthe first content from the received multiplexed data; obtaining thesecond content whose reproduction is permitted by the extracted secondlicense data; and reproducing the extracted first content, and thenreproducing the obtained second content based on the second license databy switching the reproduction from the first content to the secondcontent when the second content is obtained.